diff --git a/py/private/interpreter/repository.bzl b/py/private/interpreter/repository.bzl
index f070cd51b..60d89f311 100644
--- a/py/private/interpreter/repository.bzl
+++ b/py/private/interpreter/repository.bzl
@@ -309,9 +309,15 @@ config_setting(
         exec_compatible_with = info["compatible_with"] + extra_exec_compatible
 
         content.append("""
+# The Python interpreter toolchain has no exec_compatible_with: the interpreter
+# runs on the TARGET platform (inside the virtualenv), not on the exec host.
+# Setting exec_compatible_with = platform_constraints would prevent this
+# toolchain from being selected during cross-compilation (e.g. building an
+# arm64 image on an amd64 host), because the exec platform (amd64) would not
+# satisfy the arm64 exec constraint.  The target_compatible_with constraint is
+# sufficient to pick the right interpreter for the target.
 toolchain(
     name = "{name}",
-    exec_compatible_with = {exec_compatible_with},
     target_compatible_with = {target_compatible_with},
     target_settings = {target_settings},
     toolchain = "@{repo}//:runtime_pair",
@@ -323,7 +329,7 @@ toolchain(
 # binary on the build host regardless of the target platform being built for.
 toolchain(
     name = "{name}_exec_tools",
-    exec_compatible_with = {target_compatible_with},
+    exec_compatible_with = {exec_compatible_with},
     toolchain = "@{repo}//:exec_tools_toolchain",
     toolchain_type = "@aspect_rules_py//py/private/toolchain:exec_tools_toolchain_type",
 )